This invention relates to thermal insulation, and particularly to a thermal insulation system for protecting an elongate substrate such as a metal pipe or other fluid conduit.
Oftentimes, a requirement arises for a flexible material which can be used to resist both thermal and radiative conduction of energy. For example, such material can be formed into flexible tubing of the kind commonly used to protect components such as electrical wiring, brake and fuel lines from heat, particularly the heat sources found in automotive engine compartments. An important requirement for such tubing is flexibility, which for present purposes includes the properties of bendability, the ability to stretch circumferentially, shape retention, and ease of installation, together with the ability to resist heat transfer to the substrate to be protected. Such flexible materials may, in addition to their ability to keep items cool, alternatively be used to keep items warm by resisting heat transfer away therefrom.
A currently used product for providing such protection and insulation is a tube or sleeve comprising a foamed substrate, which is comprised of a material such as PVC/nitrile or urethane. Such a product can be quite effective in insulating against thermally conducted heat, but typically provides little protection from radiant heat. In use, where a radiant heat source is in close proximity, the foam tube has a tendency to degrade and disintegrate, falling away and thus exposing the hose or other protected component. Some attempts to reinforce the tubing to prevent such disintegration have involved, for example, the use of a polymeric transfer film. This approach has been found to offer little protection from radiant heat. Other attempts to prevent foam disintegration have involved the use of materials such as glass fabrics and graphite paper, which have been found to render the sleeve stiff and inflexible.
Prior art attempts to remedy these problems with foamed insulation have typically involved the use of an aluminized wrap of some kind, over a fiberglass insulation layer, the wrap being secured using VELCRO(copyright) hook and loop fastener or tape closures. The purpose of the metalized or aluminized wrap is to impart reflective properties to the sleeving, in order to more effectively protect against heat radiated at infra-red wavelengths. More recently, as disclosed in U.S. Pat. No. 5,718,956 to Gladfelter et al., which is assigned to Bentley-Harris, Inc., of Exton, Pennsylvania, a sleeving product for brake fluid lines, and the like, has been developed which comprises an inner tubular layer of flexible foamed insulating material, and an exterior cover layer comprising a flexible polymeric film to the surface of which a nonporous, thin coating of heat reflective metal has been applied, by vacuum deposition methods or the like, wherein the metal is for the purpose of resisting radiative heat conduction.
The problem with the prior art insulation systems, even those which include reflective components for resisting radiative heat conduction, are that they are difficult to manufacture, and to adapt to variously sized and configured systems. They also can be bulky and add substantial weight to the underlying components which require the afforded thermal protection. Additionally, over time, and because these systems are inherently disposed in hostile environments, the insulation has a tendency to fall off of the substrate, resulting in rapid system failures, and overall device breakdowns as a result of the overheating of the no longer thermally protected component.
The present invention solves the problems outlined above by providing a thermal insulation system which includes two separate components for providing protection against both thermal and radiative conduction of energy, is easily in stalled, capable of easily fitting multiple substrate diameters, space-saving and lightweight, and durable.
More particularly, the invention provides a thermal insulation system for protecting against thermal and radiative conduction of energy, comprising an inner layer of heat shrink foam and an outer layer of reflective material. In the preferred embodiment, the outer layer of reflective material is heat shrink metalized material which has been recovered using known techniques onto the inner layer of heat shrink insulative material.
In another aspect of the invention, there is provided a method of thermally insulating a substrate, such as a brake fluid line for a vehicle, which comprises the steps of heat shrinking an inner layer of material onto the substrate and disposing an outer layer of reflective material onto the inner layer. Preferably, the disposing step involves heat shrinking the outer layer onto the inner layer, thereby advantageously avoiding the use of mechanical closures or adhesive, and permitting the adaptation of the thermal insulation system to a number of differently sized substrates.
In yet another aspect of the invention, there is provided a thermal insulation system for providing protection against thermal and radiative conduction of energy, which comprises a substrate, an inner layer of heat shrink material recovered onto the substrate, and an outer layer of reflective material disposed on the inner layer of material.
In still another aspect of the invention, a brake system for a vehicle comprises a brake fluid line, an inner layer of heat shrink foam recovered onto the brake fluid line, and an outer layer of heat shrink metalized material recovered onto the inner layer of foam.